KR100525148B1 - Plasma addressed liquid crystal display - Google Patents

Abstract

An improved plasma address liquid crystal display is described so as to prevent deterioration of the liquid crystal and the alignment layer due to ultraviolet rays generated by the plasma discharge. This plasma address liquid crystal display comprises a liquid crystal cell comprising a signal electrode column, a plasma cell comprising a discharge channel row, and intermediate thin glass for bonding the liquid crystal cell to the plasma cell. The thin glass has a function of absorbing or reflecting ultraviolet rays generated in the discharge channel on the plasma cell side and includes an ultraviolet ray preventing layer for preventing the ultraviolet rays from entering the liquid crystal cell side.

Description

Plasma Address Liquid Crystal Display {PLASMA ADDRESSED LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma address liquid crystal display having a flat panel structure in which a liquid crystal cell is laminated on a plasma cell through a thin glass sheet. In particular, the liquid crystal cell is degraded by ultraviolet rays generated on the plasma cell side. It relates to a technique for preventing that.

Plasma address liquid crystal displays are disclosed, for example, in Japanese Patent Application Laid-Open No. 4-265931. 2 shows the structure of a plasma address liquid crystal display. As shown in this figure, this plasma address liquid crystal display has a flat panel structure comprising a liquid crystal cell 1, a plasma cell 2 and a common thin glass 3 interposed therebetween. This thin glass 3 is called " microsheet " because its thickness is very thin, about 50 mu m. This plasma cell 2 has a lower glass substrate 4 associated with the thin glass 3, and ionizable gas is sealed in the gap between them. Strip-type discharge electrodes are formed on the inner surface of the lower glass substrate 4. These discharge electrodes may be composed of an anode A and a cathode K arranged alternately. The discharge electrodes can be finely printed and fired on the flat glass substrate 4 with high productivity and high workability by screen printing or the like. A partition wall 7 is formed on the anode A of these discharge electrodes in order to divide the gap filled with the ionizable gas into the discharge channels 5. In addition, the partition wall 7 can be formed and baked by screen printing in such a manner that the upper part of the partition wall 7 is in contact with one surface side of the thin glass 3. In this way, the discharge channels 5 are surrounded by the horizontal plane of the glass substrate 4, the horizontal plane of the thin glass 3 and the vertical sides of the dividing walls 7. As described above, the strip-shaped discharge electrodes act as alternatingly arranged anodes A and cathodes K, causing plasma discharge therebetween. This plasma discharge generates ultraviolet rays. In addition, the thin glass 3 is bonded to the lower glass substrate 4 by a glass frit or the like.

The liquid crystal cell 1 has a transparent upper glass substrate 8. The glass substrate 8 adhere | attaches the predetermined gap generate | occur | produced between these on the other surface side of the thin glass 3 using sealing material etc., and is bonded. The gap is filled with liquid crystal 9 and filled. The liquid crystal 9 is composed of, for example, a nematic liquid crystal that is twisted at 90 degrees. The signal electrodes 10 are formed on the inner surface of the upper glass substrate 8. The signal electrodes 10 are perpendicular to the stripped discharge channels 5, and matrix-like pixels are formed at the intersection between the signal electrodes 10 and the discharge channels 5. The flat panel structure having the above configuration is configured as a transmission type structure, in which the plasma cell 2 is positioned on the light incident side and the liquid crystal cell 1 is positioned on the light exit side. A polarizer 11 is mounted on the outer surface of the plasma cell 2 to convert the illuminating lights emitted from the back light 12 into linearly polarized incident light. The analyzer 13 is mounted on an outer surface of the liquid crystal cell 1 to inspect linearly polarized outgoing light passing through the liquid crystal cell 1.

In the plasma address liquid crystal display having the above-described configuration, a switchable scanning is performed on a row of discharge cells 5 having a function of performing plasma discharge in a line-sequential manner, and the liquid crystal cell 1 is synchronized with this scanning. The display can be performed by supplying an image signal to the column of signal electrodes 10 on the side. When plasma discharge occurs in one discharge channel, the interior of the discharge channel is in a nearly constant anode potential state, thus making pixel selection for one row. In other words, the discharge channel 5 acts as a sampling switch. When the image signal is supplied to respective signal electrodes corresponding to the selected pixel with the plasma sampling switch turned on, the relevant pixels are sampled. Therefore, the lighting-on or lighting-off state of the pixel can be controlled. After this plasma sampling switch is turned off, the signal voltage is maintained at the pixel. More specifically, the liquid crystal cell 1 converts incident polarization into exit polarization according to the signal voltage to perform image display. In order to achieve this object, the liquid crystal 9 is composed of, for example, a nematic liquid crystal oriented in a twist. In order to align with this liquid crystal 9, an alignment film 14 is formed on the inner surface of the upper glass substrate 8, and the alignment film 15 is in contact with the liquid crystal 9. Form on the surface of the.

In the plasma address liquid crystal display, the liquid crystal cell 1 is addressed by scanning the discharge channels 5 on the plasma cell 2 side. Plasma discharge is generated during the scanning of the plasma channel 5. At this time, the plasma discharge generates ultraviolet rays. In the technique associated with the plasma address liquid crystal display, ultraviolet rays generated by the plasma discharge penetrate the intermediate thin glass 3 and enter the liquid crystal cell 1 directly. The liquid crystal cell 1 includes organic materials composed of the liquid crystal 9, the alignment films 14 and 15, and the like. In general, ultraviolet light deteriorates organic materials composed of the liquid crystal 9 and the alignment films 14 and 15. This lowers the voltage retention ratio of the liquid crystal 9 and / or changes the pre-tilt angle of the liquid crystal 9 oriented in a twist. As a result, there arises a problem of an after-image phenomenon due to the unevenness of the voltage retention in the screen and a change of the voltage / transmittance characteristic of the liquid crystal.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved plasma address liquid crystal display capable of preventing deterioration of liquid crystals and alignment films caused by ultraviolet rays generated by plasma discharge.

In order to achieve this object, according to the first aspect of the present invention, there is provided a liquid crystal cell including a signal electrode column, a plasma cell including a discharge channel row, and an intermediate thin glass for bonding the liquid crystal cell to the plasma cell, The glass has a function of absorbing or reflecting ultraviolet rays generated in the discharge channels on the plasma cell side, thereby providing a plasma address liquid crystal display comprising an ultraviolet light transmission prevention layer that prevents ultraviolet rays from entering the liquid crystal cell side. This ultraviolet transmission prevention layer preferably contains the ultraviolet transmission prevention film apply | coated to the at least 1 surface of thin glass. In addition, the ultraviolet ray preventing film preferably contains at least TiO ₂ or ZnO.

According to a second aspect of the present invention, there is provided a method of manufacturing a plasma address liquid crystal display having the configuration described in the first aspect of the present invention, which method has a function of absorbing or reflecting ultraviolet light on one surface of the laminated glass. Pre-forming an excited UV protective film by printing, spin-coating, vapor deposition or sputtering; Bonding the plasma cells onto one side of the thin glass; And bonding the liquid crystal cell on the other surface side of the thin glass. Alternatively, the method includes applying a UV-protective film having a function of absorbing or reflecting UV light on both surfaces of the laminated glass in advance by dipping and firing the UV-protected film, on one side of the laminated glass. Bonding the plasma cell to the other side, and bonding the liquid crystal cell on the other surface of the laminated glass.

According to the plasma address liquid crystal display of the present invention, an ultraviolet ray preventing layer is provided on the thin glass provided to separate the liquid crystal cell from the plasma cell. This ultraviolet permeation prevention film prevents the ultraviolet-ray generate | occur | produced by the plasma discharge in the plasma cell side to irradiate to the liquid crystal layer and the orientation film on the liquid crystal cell side. Thereby, deterioration of a liquid crystal and an oriented film can be prevented, and the display characteristic of a liquid crystal cell can be kept stable for a long time.

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

(First embodiment)

1 is a representative partial cross-sectional view showing the first embodiment of the plasma address liquid crystal display of the present invention. Note that the portion corresponding to that portion of the prior art plasma address liquid crystal display shown in Fig. 2 is indicated using the same reference numerals for easy understanding. As shown in FIG. 1, a plasma address liquid crystal display includes a plasma cell 2 in which a liquid crystal cell 1 comprising a column of signal electrodes 10 comprises a row of discharge channels 5 through an intermediate thin glass 3. It has a flat panel structure bonded to. The intermediate thin glass 3 is preformed to have a very thin thickness of about 50 μm. The liquid crystal cell 1 has an upper glass substrate 8 adhesively bonded to the thin glass 3 so as to have a predetermined gap therebetween. This gap is enclosed with a nematic liquid crystal 9 orientated with a twist, for example, and filled. In order to control the alignment of the liquid crystal 9, the alignment film 14 is formed on the inner surface of the glass substrate 8, and the alignment film 15 is formed on the upper surface side of the thin glass 3. Each of the alignment layers 14 and 15 is made of an organic material such as a polyimide film. In addition, the plasma cell 2 has a lower glass substrate 4 which is bonded with the thin glass 3 with a predetermined gap therebetween. This gap is divided by the strip-shaped dividing walls 7 to form the discharge channels 5. The discharge channels 5 are sealed with an ionizable gas. Anode A and cathode K are formed along respective discharge channels 5. By applying a predetermined voltage between these discharge electrodes, plasma discharge occurs in the discharge channels 5. This plasma discharge generates ultraviolet rays.

According to a feature of the invention, the thin glass 3 absorbs or reflects ultraviolet rays generated in the discharge channels 5 on the plasma cell 2 side, thereby preventing the ultraviolet rays from entering the liquid crystal cell 1 side. And a ultraviolet ray preventing layer having a function. In the present embodiment, this ultraviolet ray preventing layer is composed of an ultraviolet ray preventing film 6 applied to at least one surface of the thin glass 3. The ultraviolet ray preventing film 6 contains at least TiO ₂ or ZnO. In addition to the ultraviolet transmission prevention film 6, an ultraviolet transmission prevention layer can be formed by disperse | distributing an ultraviolet reflecting material or an ultraviolet absorbing material to the thin glass 3. According to the present invention, in this manner, an ultraviolet ray preventing film 6 is formed on the intermediate thin glass 3 arranged to separate the liquid crystal cell 1 from the plasma cell 2 so that the ultraviolet rays generated by the plasma discharge are discharged. Incident on the liquid crystal 9 and the alignment films 14 and 15 is prevented. Specifically, the ultraviolet ray preventing film 6 is formed between the thin glass 3 and the alignment layer 15 disposed directly on the discharge channels 5. The ultraviolet ray preventing film 6 has a function of absorbing or reflecting ultraviolet rays, and serves to reduce deterioration of the liquid crystal 9 and the alignment layers 14 and 15 caused by ultraviolet rays.

(2nd Example)

3 is a representative partial cross-sectional view of the second embodiment of the plasma address liquid crystal display of the present invention. For easier understanding, parts corresponding to those parts of the first embodiment of FIG. 1 are denoted by the same reference numerals. In this embodiment, the ultraviolet permeation prevention film 6 is formed not on the upper surface side of the thin glass 3 but on the lower surface side of the thin glass 3. The plasma address liquid crystal display having the above configuration can be manufactured according to the following processes. First, an ultraviolet ray preventing film 6 having a function of absorbing or reflecting ultraviolet rays is previously formed on one surface of a single thin glass by printing, spin-coating, vapor deposition, or sputtering. For example, when coating the ultraviolet-ray-transmission prevention film 6 by printing or spin-coating, a liquid coating agent is apply | coated on the surface of thin glass by printing or spin-coating, and it heat-processes and bakes. The temperature at which the coating is fired is about 300 ° C. depending on the material of the coating. In this embodiment, since the ultraviolet ray preventing film 6 is formed on a single thin glass, it can be heated to a specific temperature so that the heating temperature of the coating reaches the above high temperature without any thermal adverse effect that will affect the next process. Next, the plasma cell 2 is bonded to one surface side of the thin glass 3. More specifically, the anode A, the cathode K and the dividing walls 7 are previously formed on the lower glass substrate 4 by screen printing or the like. The glass substrate 4 is then bonded with the lower surface of the thin glass 3 by glass frit or the like. In addition, a gap located between the thin glass 3 and the glass substrate 4 and enclosed by the dividing walls 7 is sealed with an ionizable gas, thereby forming the discharge channels 5. Next, the liquid crystal cell 1 is bonded to the other surface side of the thin glass 3. More specifically, an alignment film 15 made of a polyimide film or the like is formed on the upper surface of the thin glass 3. The signal electrodes 10 formed of a transparent conductive film made of ITO or the like are patterned in a strip shape on one surface side of the upper glass substrate 8. In addition, an alignment film 14 is formed. The glass substrate 8 is bonded and bonded to the upper surface of the thin glass 3 by the encapsulation material with a predetermined gap therebetween. Finally, the gap between the glass substrate 8 and the thin glass 3 is filled with the liquid crystal 9, and the plasma address liquid crystal display is completed.

Now, the method of forming the ultraviolet ray preventing film 6, which is a characteristic component of the present invention, will be described in detail below. In the present embodiment, the ultraviolet ray preventing film 6 is formed by spin-coating using a coating agent (produced by Nissan Chemical Industries, Ltd.) containing TiO ₂ having a function of reflecting ultraviolet rays. This coating is applied on the surface of the thin glass 3 by spin-coating at a predetermined rotational speed, and then temporarily cured by irradiating ultraviolet light for about 5 minutes using a high voltage lamp 140 kV. Thereafter, the resulting film is baked by heating at a temperature of 300 ° C. for 30 minutes. As a result, the ultraviolet-ray-transmission prevention film 6 which has a thickness of about 70 nm is formed stably.

As another example, using the coating produced by TONEN CORPORATION, the ultraviolet ray preventing film 6 is formed by spin-coating. The coating agent is formed by dispersing ZnO ultrafine particles in a solution in which polysilazane is dissolved in a xylene / toluene (non-volatile content: 30% by weight) solvent. This solution is applied to the surface of the thin glass 3 by spin-coating and baked at 300 ° C. for 1 hour. The ultraviolet ray preventing film 6 has a mixed composition of SiO ₂ and ZnO. By spin-coating the solution at a rotational speed of 500 rpm per 20 seconds, an ultraviolet transmission preventing film 6 having a thickness of 1,000 nm is obtained. By spin-coating the solution at a rotational speed of 1000 rpm for 20 seconds, an ultraviolet ray preventing film 6 having a thickness of 800 nm is obtained. In addition, spin-coating of the solution at a rotational speed of 1,500 rpm for 20 seconds forms an anti-UV film 6 having a thickness of about 630 nm. The ultraviolet ray preventing film 6 formed under such a condition may block ultraviolet rays having a wavelength in a range of about 360 nm or less.

(Third Embodiment)

4 is a representative partial cross-sectional view showing a third embodiment of the plasma address liquid crystal display of the present invention. For ease of understanding, parts corresponding to those parts of the first embodiment shown in FIG. 1 are denoted by the same reference numerals. In the present embodiment, the ultraviolet ray preventing film 6 is formed on both surfaces of the thin glass 3. Here, an ultraviolet ray-proof film 6 having a function of absorbing or reflecting ultraviolet light is applied in advance to both surfaces of the laminated glass 3 in a single substrate state by dipping, and then the film is fired. A thin film 3 is immersed in a solution in which TiO ₂ or ZnO particles are dispersed, and a thin film 3 coated with a coating agent is immersed by drawing, drying, and firing, thereby preventing the ultraviolet ray permeation layer 6 ). This soaking process has the advantage that the working process is simpler compared to the above-described process using spin-coating or the like.

5 is a graph showing an example of an absorption spectrum of the liquid crystal 9. In this graph, the abscissa represents the wavelength and the ordinate represents the absorbance. As is evident from the graph, this liquid crystal absorbs ultraviolet light having a wavelength in the range of 400 nm or less. Liquid crystals composed of organic materials are typically degraded by decomposition of liquid crystal bonds by ultraviolet irradiation. Degradation of the liquid crystal 9 by absorption of ultraviolet rays lowers the retention of the signal voltage.

FIG. 6 is a graph showing the change of the pre-tilt angle of the liquid crystal 9 by ultraviolet irradiation. In this graph, the abscissa represents the irradiation time of ultraviolet rays and the ordinate represents the pre-tilt angle. The pre-tilt angle represents the tilt angle of the liquid crystal molecules at the interface between the alignment films 14 and 15. In the state before the ultraviolet irradiation, the pre-tilt angle is about 4 °. This means that the molecules of the liquid crystal are controlled to be oriented in a substantially horizontal direction. However, the alignment film 15 is degraded by the irradiation of ultraviolet rays, and the pre-tilt angle moves upward. The change of the pre-tilt angle with the elapsed time changes the operating characteristics of the liquid crystal cell 1. Specifically, a problem arises in that the voltage / transmittance characteristic of the liquid crystal cell 1 changes over time.

7A and 7B are graphs showing emission spectra of the plasma discharge generated in the discharge channel 5, respectively. In these graphs, the abscissa represents the wavelength and the ordinate represents the emission intensity. In the graph of FIG. 7B, the dimension of FIG. 7A increases along the ordinate. The emission spectrum is measured on the thin glass 3. As can be seen in the graphs, two emission peaks (UV) of ultraviolet light are observed in the wavelength range below 380 nm, one at a wavelength of 254 nm and the other at a wavelength of 365 nm. Each of these peaks is an ultraviolet emission spectrum due to the trace amount of mercury contained in the discharge channel 5. In the plasma address liquid crystal display, the thin glass 3 arranged to separate the plasma cell 2 from the liquid crystal cell 1 is very thin, about 50 μm, so that it can block the ultraviolet rays generated by the discharge channels 5. Can not.

8A is a graph showing the transmittance characteristics of the thin glass 3. In this graph, the abscissa represents the wavelength and the ordinate represents the transmittance. As can be seen from this graph, the thin glass 3 cannot completely block ultraviolet rays having a wavelength in the range of 380 nm or less. For example, in the thin glass 3, about 60% of ultraviolet rays having a wavelength of 254 nm are transmitted.

FIG. 8B is a graph showing the transmittance characteristics of the thin glass 3 on which the ultraviolet ray preventing film 6 is formed. In this graph, the abscissa represents the wavelength and the ordinate represents the transmittance. This graph shows the transmittance characteristics of the thin glass 3 on which the alignment film 15 is formed in addition to the ultraviolet ray preventing film 6. As the thin glass 3, a non-alkali glass plate having a thickness of 50 µm is used. The ultraviolet ray preventing film 6 is composed of a coating agent containing TiO ₂ and has a thickness of about 90 nm. As the alignment layer 15, two types of alignment layers S1 and S2 each having a thickness of about 30 nm may be used. The alignment films S1 and S2 have different transmittance characteristics. Since the alignment film S2 has a lower transmittance characteristic than the alignment film S1, the alignment film S2 is excellent in terms of light blocking performance of ultraviolet rays. As can be seen from the graph, the use of the alignment film S1 reduces the transmittance of ultraviolet light (wavelength: 254 nm) to 14%, and the use of the alignment film S2 reduces the transmittance of ultraviolet light (wavelength: 254 nm) by 11%. To reduce. In this case, the material selection of the alignment film is somewhat effective in reducing the transmittance of ultraviolet rays. In each case, the formation of the ultraviolet ray preventing film 6 on the thin glass 3 significantly reduces the transmittance of ultraviolet rays. As the material of the ultraviolet ray preventing film 6, TiO ₂ (titanium oxide) or ZnO (zinc oxide) described above can be used.

9A is a graph showing voltage / transmittance characteristics of a plasma address liquid crystal display of the prior art. In this graph, the abscissa represents signal voltages applied to the signal electrodes 10 of the liquid crystal cell 1, and the ordinate represents the transmittance of the liquid crystal cell 1. The data represented by the mark ○ represents an initial value and the data represented by the mark ● is characteristic after being discharged for 1,400 hours. This graph shows that the pre-tilt angle of the liquid crystal 9 is changed by the irradiation of ultraviolet rays and the pre-tilt angle of the liquid crystal 9 is increased as the irradiation time of the ultraviolet rays is increased as described with reference to FIG. 6. Indicates. When the plasma address liquid crystal display of the prior art operates for a long time, the pre-tilt angle of the liquid crystal 9 is increased, so that the voltage / transmittance characteristic is shifted to the low voltage side as shown in Fig. 9A. Therefore, the setting characteristic over time cannot be reproduced.

9B is a graph showing the voltage / transmittance characteristics of the plasma address liquid crystal display including the ultraviolet ray preventing film 6. In the plasma address liquid crystal display of the present invention, as shown in the graph, the voltage / transmittance characteristic of the liquid crystal cell 1 does not change significantly even after a long time elapses. As a result, it can be seen that the ultraviolet ray preventing film 6 is sufficiently effective to stably maintain the long-term operation of the plasma address liquid crystal display.

While the preferred embodiments have been described using specific terms, this description is exemplary only. It will be appreciated that various modifications and changes can be made without departing from the spirit or scope of the following claims.

As described above, the present invention provides a UV transmission prevention film having a function of preventing the thin glass interposed between the plasma cell and the liquid crystal cell from entering or entering the liquid crystal cell side by absorbing or reflecting ultraviolet rays generated in the discharge channel on the plasma cell side. It is provided. Therefore, the liquid crystal material and the alignment film of the liquid crystal cell can be prevented from being deteriorated by ultraviolet rays, and there is an effect that the operation of the plasma address liquid crystal display can be stably maintained for a long time.

1 is a representative partial cross-sectional view of a first embodiment of a plasma address liquid crystal display of the present invention;

2 is a partial cross-sectional view showing one embodiment of a plasma address liquid crystal display of the prior art;

3 is a partial sectional view showing a second embodiment of the plasma address liquid crystal display of the present invention;

4 is an exemplary partial sectional view showing a third embodiment of the plasma address liquid crystal display of the present invention;

5 is a graph showing absorption spectra of liquid crystals;

FIG. 6 is a graph showing a change in the pre-tilt angle of a liquid crystal by irradiation of ultraviolet rays. FIG.

7A and 7B are graphs showing emission spectra of plasma discharges generated in discharge channels, respectively.

8A and 8B are graphs showing the transmittance characteristics of the thin glass and the thin glass having the ultraviolet ray preventing film formed thereon, respectively.

9A and 9B are graphs showing voltage / transmittance characteristics of liquid crystal cells, respectively.

<Explanation of symbols for the main parts of the drawings>

1: liquid crystal cell

2: plasma cell

3: laminated glass

4: bottom glass substrate

5: discharge channels

6: UV transmission prevention film

7: dividing wall

8: upper glass substrate

9: liquid crystal

10: signal electrodes

11: polarizer

12: backlight

13: Prospector

Claims (4)

A plasma address liquid crystal display comprising a liquid crystal cell in which a liquid crystal is sealed, and a plasma cell including a row-shaped discharge channel, which are bonded to each other via intermediate thin glass, At least one surface of the thin glass includes an ultraviolet ray preventing layer for absorbing or reflecting ultraviolet rays generated from the discharge channels on the plasma cell side to prevent changes in voltage / transmittance characteristics due to an increase in the pretilt angle of the liquid crystal. A plasma address liquid crystal display. The method of claim 1, And said ultraviolet ray preventing film contains at least TiO ₂ or ZnO. A plasma address liquid crystal display manufacturing method in which a liquid crystal cell containing a columnar signal electrode, a liquid crystal cell, and a plasma cell including a row discharge channel are bonded to each other via an intermediate thin glass, Forming, by printing, spin-coating, vapor deposition, or sputtering, a coating agent having ZnO ultrafine particles dispersed in TiO ₂ , polysilazane, which has a reflection function against ultraviolet rays, on one side of the thin glass in advance; Bonding a plasma cell to one surface side of the thin glass; And Bonding a liquid crystal cell to the other surface side of the thin glass Plasma address liquid crystal display manufacturing method comprising a. A method of manufacturing a plasma address liquid crystal display comprising a columnar signal electrode, and a liquid crystal cell in which a liquid crystal is encapsulated, and a plasma cell including a row discharge channel are bonded to each other via intermediate thin glass, An ultraviolet ray preventing film having a function of absorbing or reflecting ultraviolet rays on both sides of the laminated glass in advance is dipped to immerse the laminated glass in a solution in which TiO ₂ or ZnO is dispersed. Making; Bonding a plasma cell to one surface side of the thin glass; And Bonding a liquid crystal cell to the other surface side of the thin glass Plasma address liquid crystal display manufacturing method comprising a.